A polymer electrolyte fuel cell (PEFC) has a stacked structure constituted by a plurality of single cells that have a power generation function. Each of single cells has a membrane electrode assembly (MEA) including: (1) a polymer electrolyte membrane (for example, Nafion (registered trademark) membrane); (2) a pair of catalyst layers to interpose the polymer electrolyte membrane therebetween; and (3) a pair of gas diffusion layers (GDL) to interpose the pair of the catalyst layers therebetween and disperse supply gas. The MEA in one single cell is electrically connected to another MEA in an adjacent single cell via a separator. Then, a fuel cell stack is constituted by a plurality of the single cells that are stacked on top of each other. The fuel cell stack thus obtained functions as a power generation means available for various purposes.
In the fuel cell stack, the separator functions to electrically connect the adjacent single cells to each other, as described above. In addition, the surface of the separator facing the MEA is generally provided with a gas flow path. Such a gas flow path functions as a gas supply means to supply fuel gas and oxidant gas to an anode and a cathode, respectively.
The following is a simple explanation of a power generation mechanism of the PEFC. At the time of the operation of the PEFC, fuel gas (such as hydrogen gas) is supplied to an anode side of the single cell, and oxidant gas (such as air and oxygen) is supplied to a cathode side. Accordingly, electrochemical reactions represented by the following reaction formulae proceed at the anode and cathode sides, respectively, so as to generate electricity.Anode reaction: H2→2H++2e−  (1)Cathode reaction: 2H++2e−+(½)O2→H2O  (2)
In order to promote the electrochemical reactions, the GDL is required to have a gas supply function to effectively diffuse and supply fuel gas and oxidant gas to the catalyst layers. Patent Literature 1 suggests a constitution using porous foam metal as the GDL.